Crosslinked polyvinyl acetals

ABSTRACT

The invention relates to methods for producing crosslinked polyvinyl acetals, according to which a polyvinyl alcohol (A1) containing carboxyl groups is crosslinked by (i) reacting the polymer (A1) with at least one polyaldehyde of formula R 9 (CHO) n , and (ii) at least partly esterifying groups of formula (1) and formula (4a) with each other, said steps being performed in any order. The invention further relates to methods for producing crosslinked polyvinyl acetals, according to which a polyvinyl alcohol (A2) is crosslinked by (i) reacting the polymer (A2) with at least one compound of formula (6), (ii) adding at least one compound of formula (4b), (iii) adding a polyaldehyde of formula (5), and (iv) at least partly esterifying groups of formula (1) and structural units derived from the compound of formula (4b) with each other, the radicals R 7 , R 8 , R 9 , R 10 , and R 11 , and the index n being defined as indicated in the description. Also disclosed are the crosslinked polyvinyl acetals obtained by means of the inventive method and particularly appropriate areas of application of said polymers.

The present invention relates to cross-linked polyvinylcetals, methodsfor their preparation as well as their use, especially for laminatedsafety glasses.

The modification of polyvinylalcohol by means of acetylization,especially with n-butyraldehyde, is a long-known and used reaction.Films of polyvinylacetal obtained in this way, especiallypolyvinylbutyral, are because of their resistance to light as well astheir very good adhesive capability employed as intermediate layers inlaminated safety glasses, especially in automobile panes (front and sidepanes). This type of laminated glass offers a high degree of safetysince in the event of impact stress the elastic polyvinylacetal filmabsorbs the mechanical energy and should the occasion arise glasssplinters remain adhered to the film.

Unfortunately however laminated safety glasses based on conventionalpolyvinylcetal types frequently have insufficient mechanical properties,especially at higher temperatures above 150° C. This problem is onlypartially solved by use of polyvinylacetals with higher molecularweights, since at this point among others, based on processing problems(e.g. blister formation, too high or too low polyvinylcetal viscosity atthe working temperature, lack of constancy in properties during theprocessing) impacts practical feasibility mostly at the boundaries.

On this basis European Patent Application 211 818 suggests theutilization of polyvinylbutyral which by use of aldehydes having atleast two aldehyde groups cross-linked via intermolecular diacetallinkages are cross-linked with the butyraldehyde before or during theacetylization reaction of polyvinylalcohol. Due to the very highreactivity of aldehydes this type of cross-linking leads however tostrong cross-linking, very high molecular weights and thereforepartially insoluble polyvinylbutyrals, which have only limited—ifany—suitability for the manufacture of high quality laminated safetyglasses. Independently of that the polyvinylbutyrals cross-linkedthrough di- or polyaldehydes under the conditions of thermoplasticprocessing of polymers (e.g. extrusion) are not sufficiently stablewhich is why, depending on the applied temperatures, dwell times, shearrates etc. a more or less strongly pronounced splitting of thecross-linking points (molecular weight breakdown) takes lace. This lackof thermal stability especially complicates the manufacture ofreproducible product qualities, since the polymer reacts extremelysensitively to process fluctuations, and results moreover in a worseningof the mechanical properties of the polyvinylacetals especially at hightemperatures.

In consideration of this state of the art therefore it was an object ofthe present invention to provide polyvinylacetals with improvedmechanical properties, especially at higher temperatures, preferablyabove 150° C. In this context in accordance with the invention thepolyvinylacetals should be suitable for the manufacture of films as wellas especially the manufacture of laminated safety glasses of higherquality, and based on this preferably have a better constancy of thematerial properties, especially mechanical properties, in processing tofilms and to laminated safety glasses.

The present invention had the basic object to specify a method for themanufacture of polyvinylacetals in accordance with the invention of asimple type and way, which can be carried out cost-effectively on alarge scale.

A further object of the invention was to identify and demonstrateparticularly suitable application areas for the polyvinylcetals inaccordance with the invention.

These, as well as other not explicitly stated objects, are solved, whichhowever may be inferred or deduced without need for further discussionfrom the interrelationships discussed herein, through cross-linkedpolyvinylacetals, which are obtainable by means of a manufacturingmethod with all features of the present Patent Claim 1 or 5. Appropriatemodifications of the method in accordance with the invention areprotected in the dependent claims related to Claim 1 and/or 5.Furthermore the polyvinylcetals obtainable by means of the method inaccordance with the invention, as well as for the application ofspecially interesting claimed application designs and application areas.

Thus that one includes a first method for preparation of cross-linkedpolyvinylcetals, in which the polymer (A1), relative to its totalweight, contains

-   (a) 1.0 to 99.9 wt % structural units of formula (1)

wherein R¹ represents hydrogen or methyl

-   (b) 0 to 99.0 wt % structural units of formula (2)

-   -   wherein R² represents hydrogen or an alkyl group with 1 to 6        carbon atoms,

-   (c) 0 to 70.0 wt % of structural units of formula (3)

-   -   wherein R³, R⁴, R⁵ and R⁶, are in each case groups independent        of each other with a molecular weight in the range from 1 to 500        g/mol,

-   (d) 0.00001 to 30.0 wt % structural units of formula (4a)

-   -   wherein R⁷ is a linkage, an alkylene group with 1 to 10 carbon        atoms or an if necessary substituted arylene group with 6 to 12        carbon atoms and R⁸ is hydrogen, COOH, an alkyl group with 1 to        10 carbon atoms or an if necessary substituted aryl group with 6        to 12 carbon atoms,        wherein one in any sequence,

-   (i) reacts polymer (A1) with at least one polyaldehyde of formula    (5),    R⁹(CHO)_(n)  (5)    -   wherein R⁹ represents a linkage or a group having 1 to 40 carbon        atoms and n is a whole number greater than 2, and

-   (ii) at least partially, groups of formula (1) and formula (4a)    esterified with each other,    and a second method for manufacture of cross-linked polyacetals    provided in which a polymer (A2) is cross-linked, which relative to    its total weight, contains

-   (a) 1.0 to 99.9 wt % structural units of formula (1)

-   (b) 0 to 99.0 wt % structural units of formula (2)

-   (c) 0 to 70.0 wt % of structural units of formula (3)    wherein one

-   (i) reacts the polymer (A2) with at least one compound of formula    (6)

-   -   wherein R¹⁰ and R¹¹, in each case independent of each other, are        hydrogen, an alkyl group with 1 to 10 carbon atoms or an if        necessary substituted aryl group with 6 to 12 carbon atoms,

-   (ii) adds at least one compound of formula (4b),

-   -   wherein R⁷ is a linkage, an alkylene group with 1 to 10 carbon        atoms or an if necessary substituted arylene group with 6 to 12        carbon atoms and R⁸ is hydrogen, COOH, an alkyl group with 1 to        10 carbon atoms or an if necessary substituted aryl group with 6        to 12 carbon atoms,

-   (iii) adds a polyaldehyde of given formula (5), and

-   (iv) esterifies at least partially groups of formula (1) and    structural units derived from the compound of formula (4b) with each    other,

It succeeds with no further ado to make cross-linked polyvinylacetals ina predictable way, which in particular have improved mechanicalproperties at high temperatures preferably above 150° C., and above allhave a better memory.

At the same time the cross-linked polyacetals in accordance with theinvention have a series of other advantages. Belonging here amongstothers are:

-   -   The polyacetals in accordance with the invention are        distinguished by an improved constancy of material properties,        such as for example their memory. This advantage is especially        observed at temperatures higher than 150° C. A change in        cross-linking density as in European Patent 211 818 can within        the scope of the present invention not be observed, on the        contrary the poyvinylacetals in accordance with the invention        also have a significantly improved constancy of their        cross-linking density at temperatures above 150° C.    -   The presence of the polymer-bound carboxyl or carboxylate groups        in the polymers in accordance with the invention leads to a        distinct stabilization of the junction points developed via        acetal cross-links. Moreover they fulfill a buffer function and        in this way possibly have harmful acid-effects for example by        hydrolysis products effective toward anti-adhesive agents.    -   The cross-linked polyacetals in accordance with the invention        can be simply produced cost-effectively on a large scale. In        that connection especially through taking care of the        cross-linking conditions and the necessarily short cross-linking        times, oxidation reactions and/or other additional thermally        induced reactions, which as a rule lead to coloration of the        polymer and thus particularly for the application as transparent        laminated safety glass, is a loss of quality that is to be        avoided.    -   The manufacture of the cross-linked polyacetals in accordance        with the invention can be carried out with care very quickly so        that based on the high molecular weights of the        polyvinylacetals, already at the beginning, very short extrusion        distances or extrusion holding times can be selected.    -   Based on its characteristic property profile the        polyvinylacetals in accordance with the invention are especially        suitable for laminated safety glass which can be manufactured        cost-effectively on a large scale in a simple way, especially by        means of an extrusion process. Thereby in this connection above        all the advantage to carry, that through use of the        polyvinylcetals in accordance with the invention, blister        formation as well as property fluctuations during the processing        are as far as possible avoided and in this way laminated safety        glasses with improved optical and mechanical properties, and        better reproducibility, are feasible.

According to a first aspect the present invention relates to polyacetalswhich are obtainable from a polymer (A1), which in relation to its totalweight, contain

-   (a) 1.0 to 99.9 wt % structural units of formula (1)

-   (b) 0 to 99.0 wt % structural units of formula (2)

-   (c) 0 to 70.0 wt % of structural units of formula (3)

-   (d) 0.00001 to 30.0 wt %, preferably 0.1 to 30.0 wt %, structural    units of formula (4a)

Thereby the particular structural units differ naturally from eachother, comprised especially in the framework of the present inventionthe structural unit of the formula (3) not the structural units of theformula (1), (2) and/or (4a).

The group R¹ represents, in each case independently of each other,hydrogen or methyl, preferably hydrogen.

The group R² identifies hydrogen or an alkyl group with 1 to 6 carbonatoms, preferably an alkyl group with 1 to 6 carbon atoms, suitably amethyl, ethyl, n-propyl, iso-propyl,

n-butyl, sec-butyl, tert-butyl, n-pentyl, or an n-hexyl group,advantageously a methyl or an ethyl group, especially a methyl group.

The groups R³, R⁴, R⁵, R⁶ are in each case groups that are independentof each other with a molecular weight in the range from 1 to 500 g/mol,suitably hydrogen, an if necessary branched aliphatic or cycloaliphaticgroup with 1 to 16 carbon atoms, which if necessary can contain one or aplurality of carboxylic acid amides—and/or sulfonic acid groups.

The group R⁷ is a linkage, an alkylene group with 1 to 10 carbon atomsor an if necessary substituted arylene group with 6 to 12 carbon atoms,suitably hydrogen or a methylene, ethylene, n-propylne, iso-propylene,n-butylene, sec-butylene, tert-butylene, n-pentylene, or an n-hexylenegroup, which can if necessary have one or a plurality of COOH groups assubstituents.

The group R⁸ represents hydrogen, a carboxyl group or an alkyl groupwith 1 to 10 carbon atoms or an if necessary substituted aryl group with6 to 12 carbon atoms, suitably hydrogen or a methyl, ethyl, n-propyl,iso-propyl, n-butyl, sec-butyl, tert-butyl, n-pentyl, or an n-hexylgroup, which can if necessary have one or a plurality of COOH groups assubstituents. Specially preferred R⁸ groups comprise hydrogen, a methylgroup and —CH₂COOH.

Specially preferred structural units of formula (3) derive from straightchain or branched olefins with 2 to 18 carbon atoms, (meth)acrylamidesand/or ethylenesulfonic aid. In this context olefins such as those withan end-positioned C—C double bond, which preferably has 2-6 carbonatoms, especially ethylene prove to be especially favorable. Furthermorestructural units (3) which derive from acrylamidepropenylsulfonic acid(AMPS) lead in accordance with the invention to quite especiallyadvantageous results.

Specially preferred structural units of formula (4) are obtainable byacetalization of structural units of formula (1) with glyoxalic acid.

In accordance with a second aspect the present invention relates topolyacetals which are obtainable from a polymer (A2), which contain inrelation to its total weight,

-   (a) 1.0 to 99.9 wt % structural units of formula (1)-   (b) 0 to 99.0 wt % structural units of formula (2)-   (c) 0 to 70.0 wt % structural units of formula (3)

Thereby the particular structural units differ naturally from eachother, comprised especially within the framework of the presentinvention, the structural unit of the formula (3) not the structuralunits of the formula (1), and/or (2).

Furthermore the groups R¹ to R⁶ are defined as described earlier.

Relative to the composition of the polymers (A1) and/or (A2), thefollowing is preferably applicable:

The total number of structural units of formula (2) is preferably in therange from 0.1 to 40 mol %, suitably in the range from 0.5 to 25.0 mol%, especially in the range from 1.0 to 15.0 mol %, in each case relativeto the total number of structural units of the formula (1) and (2)Thereby, in accordance with a first preferred embodiment of the presentinvention, polymers (A1) and/or (A2) are employed, which relative to thetotal number of structural units of formula (1) and (2) contain 1.0 to2.0 mol % structural units of formula (2). In accordance with a secondpreferred embodiment of the present invention polymers (A1) and/or (A2)are employed, which relative to the total number of structural units offormula (1) and (2) contain 3.0 to 7.0 mol % structural units of formula(2). In accordance with a third preferred embodiment of the presentinvention polymers (A1) and/or (A2) are employed, which relative to thetotal number of structural units of formula (1) and (2) contain 10.0 to15.0 mol % structural units of formula (2).

In accordance with another preferred embodiment of the present inventionthe polymers (A1) and/or (A2) contain, in each case relative to thetotal weight, >50.0 wt %, suitably>60.0 wt %, advantageously>70.0 wt %,especially>80.0 wt % of structural units of formula (1) and/or (2).Especially advantageous results can be obtained thereby with polymers(A1) and/or (A2), which, in each case contain relative to their totalweight>85.0 wt %, suitably>90.0 wt %, advantageously>95.0 wt %,especially>99.0 wt % of structural units of formula (1) and/or (2).

Within the scope of the present invention the polymers (A1) and/or (A2)possess a syndiotactic, isotactic and/or atactic chain structure. It anmoreover be either a random or a block copolymer.

The viscosity of polymers (A1) and/or (A2) is in accordance with theinvention of subordinate significance, in principle low as well as highmolecular weight polymers (A1) and/or (A2) can be utilized. Nonethelessit has been shown within the framework of the present invention to bequite especially favorable that the polymers (A1) and/or (A2) have aviscosity in the range from 1 to 70 mPas, especially in the range from 2to 40 mPas, especially in the range from 3 to 30 mPas (measured as a 4%aqueous solution according to Höppler at 20° C., DIN 53015).

Furthermore, the polymers (A1) and (A2) are not subject to any speciallimitations relative to their molecular weight, for the purposes of thepresent invention however polymers (A1) and/or (A2) have quite speciallystood the test of a mid-range molecular weight of at least 20,000 g/mol.The mid-range molecular weight is preferably determined thereby by meansof gel permeation chromatography, suitably using a polyethylene oxidecalibration.

The manufacture of polymers (A1) and/or (A2) for use in accordance withthe invention, can be carried out in a known way by means of amulti-stage method. In a first step the corresponding vinyl esterdissolved in a suitable solvent, as a rule water or an alcohol likemethanol, ethanol, propanol and/or butanol is radically polymerized byuse of a suitable radical starter. If the polymerization is carried outin the presence of radically copolymerizable monomers then one obtainsthe corresponding vinyl ester copolymers.

In a second step the vinyl ester (co)polymer is then saponified,conventionally by transesterfication with methanol, wherein the desireddegree of saponificaton can be adjusted in a known way, for example byvariation of the catalyst concentration, the reaction temperature and/orthe reaction time. For further details refer to the current technicalliterature, in particular Ullmann's Encyclopedia of IndustrialChemistry, Fifth Edition on CD-ROM, Wiley-VCH, 1997, Keyword:Poly(VinylAcetals) and the references given therein.

Starting from the polyvinylalcohol obtained in this manner the polymers(A1) can then be obtained by esterification and acetalization with acompound if formula (4b),

-   -   wherein R⁷ is a linkage, an alkyl group with 1 to 10 carbon        atoms or an if necessary substituted arylene group with 6 to 12        carbon atoms and R⁸ is hydrogen, COOH, an alkyl group with 1 to        10 carbon atoms or an if necessary substituted aryl group with 6        to 12 carbon atoms.

The reaction of polyvinylalcohol with the compound (4b) is preferablycarried out in at least one inert solvent, wherein the term “inertsolvent” holds for such a solvent, which under the particular reactionconditions does not disturb or even hinder the course of the desiredreaction. An especially appropriate solvent in this connection is water.

Furthermore, the reaction may be carried out thereby in a favorablemanner in the presence of acid catalysts. Suitable acids comprise inaddition to organic acids such as for example acetic acid, mineral acidslike hydrochloric acid, sulfuric acid and/or nitric acid, wherein theaddition of hydrochloric acid, sulfuric acid and/or nitric acid has beenespecially proved in the art. Carrying out the reaction occurs in such away that an aqueous solution is prepared of the polyvinyl alcohol, thecompound (4b) is put into this solution and subsequently the acidcatalyst is added drop-wise.

Within the framework of a first embodiment of the present invention thecross-linked polyvinylacetals are obtained, in which one in anysequence,

-   (i) reacts polymer (A1) with at least one polyaldehyde of formula    (5),    R⁹(CHO)_(n)  (5)    -   and-   (ii) at least partially, groups of formula (1) and of formula (4a)    esterify with each other.

In that connection R⁹ represents a linkage or a group having 1 to 40carbon atoms, preferably an aliphatic, cycloaliphatic and/or aromaticgroup with suitably 1 to 20, preferably 1 to 12, especially 2 to 10carbon atoms.

The index n is a whole number larger than 2, preferably in the rangefrom 2 to 10, suitably in the range from 2 to 6, especially 2 or 3. Inaccordance with a quite specially preferred embodiment of the inventionn equals 2.

In accordance with the invention quite especially suitable compounds offormula (5) comprise glyoxyl, propanedial, n-butanedial,glutardialdehyde, n-hexanedial, n-heptanedial, n-octanedial,n-nonanedial, n-decanedial, n-undecanedial, n-dodecanedial,4,4′-ethylenedioxydibenzaldehyde and 2-hydrtoxyhexanedial, especiallyglutardialdehyde and n-nonanedial.

The amount of polyaldehyde (5) can within the framework of the presentinvention be in principle chosen at will, however it has been proven forthe purposes of the present invention to be quite special to add 0.001to 1.0 wt %, suitably 0.005 to 2.0 wt %, especially 0.01 to 1.0 wt % ofpolyaldehyde (5) in relation to the total polymer weight.

Carrying out of steps (i) and (ii) can be carried out in any order, thatis it is possible to initially carry out step (i) and then step (ii) orfirst step (ii) and then step (i) or however both steps simultaneously.However for the purposes of the present invention it has been shownquite especially favorable to first carry out step (i) and then step(ii).

Within the framework of a quite specially preferred embodiment of thepresent invention, at any point in time, at least one compound offormula (6) is added.

The groups R¹⁰ and R¹¹ are independently of each other hydrogen, analkyl group with 1 to 10 carbon atoms or an aryl group with 6 to 12carbon atoms. In that connection, these alkyl and aryl groups can besubstituted with one or a plurality of hydroxyl, sulfonic acid groupsand/or halogen atoms, such as fluorine, chlorine, bromine or iodine.Formaldehyde, acetaldehyde, propionaldehyde, n-butyraldehyde,iso-butyraldehyde, iso-butyraldehyde, 2-ethoxybutyraldehyde,paraldehyde, 1,3,5-trioxane, capronaldehyde, 2-ethylhexanal,pelargonaldehyde, 3,5,5-trimethylhexanal,

2-formylbenzosulfonic acid, acetone, ethylmethylketone, butylethylketoneand/or ethylhexylketone belong to the preferred compounds of formula(6).

Within the framework of the present invention the addition of aldehydesthat is of compounds of formula (6) with R¹⁰=hydrogen and R¹¹=hydrogen,a methyl, ethyl, n-propyl or an isopropyl group, preferably offormaldehyde and/or n-butyraldehyde, especially of n-butyradehyde haveproved themselves quite especially.

The ratio of the components (5) and (6) is preferably chosen as follows

-   (1) 95.00 to 99.9 parts by weight at least of a compound (6)-   (2) 0.01 to 5.0 parts by weight of at least one polyaldehyde (5),    wherein the added parts by weight preferably round out to 100.00    parts by weight.

The reaction of polymer (A1) with the compound (5) and/or (6) ispreferably carried out in at least one inert solvent, wherein the term“inert solvent” holds for such a solvent, which under the particularreaction conditions does not disturb or even hinder the course of thedesired reaction. A partiularly suitable solvent in this connection iswater.

The reaction may furthermore be carried out in a favorable manner in thepresence of acid catalysts. Suitable acids comprise in addition toorganic acids such as for example acetic acid, mineral acids likehydrochloric acid, sulfuric acid and/or nitric acid, wherein theaddition of hydrochloric acid, sulfuric acid and/or nitric acid has beenespecially proved in the art. Carrying out the reaction takes placepreferably in such a way that an aqueous solution is prepared of polymer(A1), the compound (5) and/or (6) is put into this solution andsubsequently the acid catalyst is added drop-wise.

Within the framework of a second embodiment of the present invention thecross-linked polyvinylacetals are obtained, in which one,

-   (i) reacts the polymer (A2) with at least one compound of formula    (6),-   (ii) adds at least one compound of formula (4b),-   (iii)adds a polyaldehyde of formula (5), and-   (iv) esterifies at least partially groups of formula (1) and    structural units derived from the compound of formula (4b)

In that connection the compounds of formula (4b), (5) and (6) aredefined as above.

The esterification (ii) and/or (iv) can be performed in a known way,wherein it has been shown within the framework of the present inventionto be quite especially favorable to carry out the cross-linkingthermally, if necessary in the presence of at least one softener, atbulk temperatures in the range from 80 to 280° C., preferably in therange from 120 to 280° C., and especially in the range from 140 to 260°C.

The thermal cross-linking of polyacetal can be carried out thereby withany heatable units known to the person skilled in the art, such as forexample ovens, kneaders, extruders, presses or autoclaves. Preferablyhowever thermal cross-linking is carried out in extruders or in kneadingunits, since these ensure a good homogenization with the softener(s)which is/are contained in a preferred embodiment. The cross-linking isthereby recognizable for that in comparison with the non cross-linkedhigher molecular weight of cross-linked polyacetal.

The degree of cross-linking can be freely chosen—according to theapplication. Nonetheless, within the framework of the present invention,it has been shown to be quite especially suitable that at least 10 mol%, preferably at least 20 mol %, suitably at least 30 mol %, especiallyat least 40 mol %, of all carboxyl groups contained originally in thepolyvinylacetal be esterified. Thereby the carboxyl group contentrelative to the total weight of cross-linked polyacetal is preferablyless than 10.0 wt % and lies preferably in the range from 0.00001 to10.0 wt %, specially preferred in the range from 0.001 to 10.0 wt %,suitably in the range from 0.01 to 5.0 wt % and especially from 0.01 to2.0 wt %.

The cross-linked polyvinylacetals in accordance with the inventioncontain softeners in a preferred embodiment. Any softener known to theperson skilled in the art can be employed as a softener. The softener isthus added in the customary amount known to the person skilled in theart. Known softeners for polyvinylacetals, especially forpolyvinylbutyrals are thereby the esters of aliphatic mono- anddicarboxylic acids with single or multivalent alcohols or oligoalkyleneglycol ethers, phosphoric acid esters as well as various phthalates,such as are disclosed in this connction in for example U.S. Pat. No.5,137,954. Preferably employed however are the diesters of di-, tri- andtetraethyleneglycols with aliphatic monocarboxylic acids, adipicacid-dialkyl ester as well as the dibenzoates of alkylene- andpolyalkylene glycols described in the un-prepublished German PatentApplication 101 00 681.

Possible addition areas of cross-linked polyvinylacetals in accordancewith the invention are apparent to one skilled in the art. They areespecially suited for all applications, which are indicated forcross-linked polyvinylacetals, especially for polyvinylformals and/orpolyvinylbutyrals. Especially preferred application areas comprise theiruse as films, especially for laminated glasses, which can preferably bemade by direct extrusion with the help of wide slit nozzles. Furtherdetails for the extrusion of polyvinylacetals and for the manufacture ofpolyvinylacetal—especially polyvinylutyral films, are sufficiently knownto the person skilled in the art from the technical literature.

In the context of the present invention, a specially preferredapplication area for the polyvinylacetals in accordance with theinvention are flat shapes, especially films, preferably with a thicknessin the range from 0.5 μm to 1 mm. The films in accordance with theinvention can thereby contain other usual additives, such as e.g.oxidation stabilizers, UV stabilizers, dyestuffs, filler materials,pigments and/or anti-adhesion agents.

Furthermore the polyvinylacetals in accordance with the invention arespecially suited for the coating of substrates, especially wood, metal,plastic, glass, textiles, paper, and leather, as well as ceramic andmineral undercoats. The object of the present invention is thereforealso coatings containing polyvinylcetals in accordance with theinvention.

The coatings can moreover contain polymer resins, softeners, pigments,filler materials, stabilizers, adhesion promoters, rheological aids,additives that influence pH, and/or additives which catalyze chemicalreactions between the polyvinylacetals in accordance with the inventionand other polymer resins as well as between the other polymer resins andeach other.

The coating in accordance with the invention can take place in a knownway either as powder which preferably is subsequently melted at a highertemperature and cross-linked, or also from a preferably organic solutionby means of coating methods known to a person skilled in the art.Thereby, in applying from solution, the polyvinylcetal to becross-linked in accordance with the invention, if necessary togetherwith other binding agents, as well as if necessary other ingredients,such as for example softeners, pigments, filler materials, stabilizers,adhesion promoters, rheological aids, dissolved in the solvent orsolvent mixture is then preferably applied to the substrate to becoated. The cross-linking in accordance with the invention is preferablycarried out after evaporation of the solvent, suitably at a temperaturein the region of 20 to 200° C. Thereby the cross-linking reaction isfavorably supported by pH-lowering additives, such as for exampleorganic and/or inorganic acids.

In connection with its application in coatings the cross-linking becomesevident in an increase in the resistance to solvents as well as anincrease of molecular weight, in the comparison with non cross-linkedpolyvinylcetal.

In accordance with another aspect of the present invention thepolyvinylacetals in accordance with the invention are also especiallysuitable for the manufacture of ionically conductive intermediate layersfor electrochromic systems.

1. A method for the manufacture of cross-linked polyvinylacetals, saidmethod comprising, in any sequence: (i) reacting a polymer (A1) whichcontains in relation to its total weight (a) 1.0 to 99.9 wt % structuralunits of formula (I)

 where R¹ represents hydrogen or methyl, (b) 0 to 99.0 wt % structuralunits of formula (2)

 wherein R² represents hydrogen or an alkyl group with 1 to 6 carbonatoms, (c) 0 to 70.0 wt % of structural units of formula (3)

 wherein R³, R⁴, R⁵ and R⁶, are in each case groups independent of eachother with a molecular weight in the range from 1 to 500 g/mol, and (d)0.00001 to 30.0 wt % structural units of formula (4a)

 wherein R⁷ is a linkage, an alkylene group with 1 to 10 carbon atomsoptionally substituted by one or more COOH groups, or an optionallysubstituted arylene group with 6 to 12 carbon atoms, and R⁸ is hydrogen,COOH, an alkyl group with 1 to 10 carbon atoms and optionallysubstituted by one or more COOH groups, or an optionally substitutedaryl group with 6 to 12 carbon atoms, with at least one polyaldehyde offormula (5),R⁹(CHO)_(n)  (5)  wherein R⁹ represents a linkage or a group having 1 to40 carbon atoms, and n is a whole number greater than 2; and (ii) atleast partially esterifying groups of formula (1) and formula (4a) ofpolymer (A1) with each other.
 2. The method according to claim 1,further comprising adding at any point in time at least one compound offormula (6),

wherein R¹⁰ and R¹¹ are each independently hydrogen, an alkyl group with1 to 10 carbon atoms which is optionally substituted by one or morehydroxyl, sulfonic acid groups, halogen atoms, or combinations thereof,or an aryl group with 6 to 12 carbon atoms which is optionallysubstituted by one or more hydroxyl, sulfonic acid groups, halogenatoms, or combinations thereof.
 3. The method according to claim 1,wherein R⁸ is hydrogen.
 4. The method according to claim 1, wherein R⁷is a linkage or an alkylene group with 1 to 4 carbon atoms.
 5. A methodfor the manufacture of cross-linked polyvinylacetals, said methodcomprising: (i) reacting a polymer (A2), which in relation to its totalweight contains (a) 1.0 to 99.9 wt % structural units of formula (1)

 wherein R¹ represents hydrogen or methyl, (b) 0 to 99.0 wt % structuralunits of formula (2)

 wherein R² represents hydrogen or an alkyl group with 1 to 6 carbonatoms, and (c) 0 to 70.0 wt % of structural units of formula (3)

 wherein R³, R⁴, R⁵ and R⁶, are in each case groups independent of eachother with a molecular weight in the range from 1 to 500 g/mol, with atleast one compound of formula (6)

 wherein R¹⁰ and R¹¹ are each independently hydrogen, an alkyl groupwith 1 to 10 carbon atoms which is optionally substituted by one or morehydroxyl, sulfonic acid groups, halogen atoms, or combinations thereof,or an aryl group with 6 to 12 carbon atoms which is optionallysubstituted by one or more hydroxyl, sulfonic acid groups, halogenatoms, or combinations thereof, (ii) adding at least one compound offormula (4b)

 wherein R⁷ is a linkage, an alkylene group with 1 to 10 carbon atomsoptionally substituted by one or more COOH groups, or an optionallysubstituted arylene group with 6 to 12 carbon atoms and R⁸ is hydrogen,COOH, an alkyl group with 1 to 10 carbon atoms and optionallysubstituted by one or more COOH groups, or an optionally substitutedaryl group with 6 to 12 carbon atoms, (iii) a polyaldehyde added offormula (5),R⁹(CHO)_(n)  (5)  wherein R⁹ is a linkage or a group having 1 to 40carbon atoms and n is a whole number greater than 2, and (iv) at leastpartially esterifying groups of formula (1) and groups derived fromstructural units of formula (4b) with each other.
 6. The methodaccording to claim 5, wherein R⁸ is hydrogen.
 7. The method according toclaim 5, wherein R⁷ is a linkage or an alkylene group with 1 to 4 carbonatoms.
 8. The method according to claim 1, wherein n is 2 or
 3. 9. Themethod according to claim 1, wherein R⁹ is an aliphatic, cycloaliphaticand/or aromatic group with 1 to 12 carbon atoms.
 10. The methodaccording to claim 9, wherein glutardialdehyde and/or n-nonanedial isutilized as compound (5).
 11. The method according to claim 1, whereinn-butyraldehyde is employed as compound (6).
 12. The method according toclaim 1, wherein (1) 95.00 to 99.99 parts by weight at least of onecompound (6), and (2) 0.01 to 5.00 parts by weight at least of apolyaldehyde (5) are added, wherein the parts by weight given is basedon 100.00 parts by weight of the total amount of compound (5) andcompound (6).
 13. The method according to claim 1, whereinesterification (ii) or (iv) is carried out in presence of at least onesoftener, at a temperature of from 80 to 280° C.
 14. The methodaccording to claim 13, wherein cross-linking is carried out in anextruder, kneading device or another heatable unit.
 15. A cross-linkedpolyvinylacetal obtainable by a method in accordance with claim
 1. 16.The polyvinylacetal in accordance with claim 15, wherein the carboxylgroup content relative to the total weight of cross-linked polyacetal isless than 10.0 wt %.
 17. The polyvinylacetal in accordance with claim15, wherein said polyvinylacetal contains softeners.
 18. A moldingmaterial containing a polyvinylacetal in accordance with claim
 15. 19. Afilm containing a polyvinylacetal in accordance with claim
 15. 20. Alaminated safety glass containing a film according to claim
 19. 21. Acoating containing a polyvinylacetal in accordance with claim
 15. 22. Anionically conductive intermediate layer for electrochromic systemscomprising a polyvinylacetal in accordance with claim
 15. 23. A methodaccording to claim 1, wherein R¹ is hydrogen or methyl; R² is hydrogen,methyl, ethyl, n-propyl, iso-propyl, n-butyl, sec-butyl, iso-butyl,tert-butyl, n-pentyl, or n-hexyl; R³, R⁴, R⁵, and R⁶ are eachindependently hydrogen, an optionally branched aliphatic orcycloaliphatic group having 1 to 16 carbon atoms which is optionallysubstituted by one or more carboxylic amide groups and/or one or moresulphonic acid groups, R⁷ is methylene, ethylene, n-propylene,iso-propylene, n-butylene, sec-butylene, tert-butylene, n-pentylene, orn-hexylene, in each case optionally substituted by one or more COOHgroups; and R⁸ is hydrogen, or methyl, ethyl, n-propyl, iso-propyl,n-butyl, sec-butyl, iso-butyl, tert-butyl, n-pentyl, or n-hexyl, whichin each case optionally substituted by one or more COOH groups.
 24. Amethod according to claim 5, wherein R¹ hydrogen or methyl; R² ishydrogen, methyl, ethyl, n-propyl, iso-propyl, n-butyl, sec-butyl,iso-butyl, tert-butyl, n-pentyl, or n-hexyl; R³, R⁴, R⁵, and R⁶ are eachindependently hydrogen, an optionally branched aliphatic orcycloaliphatic group having 1 to 16 carbon atoms which is optionallysubstituted by one or more carboxylic amide groups and/or one or moresulphonic acid groups, R⁷ is methylene, ethylene, n-propylene,iso-propylene, n-butylene, sec-butylene, tert-butylene, n-pentylene, orn-hexylene, in each case optionally substituted by one or more COOHgroups; and R⁸ is hydrogen, or methyl, ethyl, n-propyl, iso-propyl,n-butyl, sec-butyl, iso-butyl, tert-butyl, n-pentyl, or n-hexyl, whichin each case is optionally substituted by one or more COOH groups.
 25. Amethod according to claim 23, wherein R⁹ is an aliphatic, cycloaliphaticand/or aromatic group having up to 20 carbon atoms, and n is a wholenumber from 2 to
 10. 26. A method according to claim 24, wherein R⁹ isan aliphatic, cycloaliphatic and/or aromatic group having up to 20carbon atoms, and n is a whole number from 2 to
 10. 27. A methodaccording to claim 1, wherein the compound of formula (5) is glyoxyl,propanedial, n-butanedial, glutardialdehyde, n-hexanedial,n-heptanedial, n-octanedial, n-nonanedial, n-decanedial, n-undecanedial,n-dodecanedial, 4,4′-ethylenedioxydibenzaldehyde or2-hydrtoxyhexanedial.
 28. A method according to claim 2, wherein thecompound of formula (6) is formaldehyde, acetaldehyde, propionaldehyde,n-butyraldehyde, iso-butyraldehyde, iso-butyraldehyde,2-ethoxybutyraldehyde, paraldehyde, 1,3,5-trioxane, capronaldehyde,2-ethylhexanal, pelargonaldehyde, 3,5,5-trimethylhexanal,2-formylbenzosulfonic acid, acetone, ethylmethylketone, butylethylketoneor ethylhexylketone.
 29. A method according to claim 1, wherein thecompound of formula (5) is glyoxyl, propanedial, n-butanedial,glutardialdehyde, n-hexanedial, n-heptanedial, n-octanedial,n-nonanedial, n-decanedial, n-undecanedial, n-dodecanedial,4,4′-ethylenedioxydibenzaldehyde or 2-hydrtoxyhexanedial, and thecompound of formula (6) is formaldehyde, acetaldehyde, propionaldehyde,n-butyraldehyde, iso-butyraldehyde, iso-butyraldehyde,2-ethoxybutyraldehyde, paraldehyde, 1,3,5-trioxane, capronaldehyde,2-ethylhexanal, pelargonaldehyde, 3,5,5-trimethylhexanal,2-formylbenzosulfonic acid, acetone, ethylmethylketone, butylethylketoneor ethylhexylketone.
 30. A method according to claim 1, wherein thetotal number of structural units of formula (2) is from 0.1 to 40 mol %,relative to the total number of structural units of the formula (1) and(2).
 31. A method according to claim 29, wherein the total number ofstructural units of formula (2) is from 0.5 to 25.0 mol %, relative tothe total number of structural units of the formula (1) and (2).
 32. Amethod according to claim 1, wherein polymer A1 contains, relative tothe total weight, >50.0 wt %, of structural units of formula (1) and/or(2).
 33. A method according to claim 5, wherein polymer A2 contains,relative to the total weight, >50.0 wt %, of structural units of formula(1) and/or (2).
 34. A method according to claim 1, wherein polymer A1has a viscosity in the range from 1 to 70 mPas.
 35. A method accordingto claim 5, wherein polymer A2 has a viscosity in the range from 1 to 70mPas.
 36. A polyvinylacetal in accordance with claim 17, wherein saidsofteners are selected from diesters of di-, tri- andtetraethyleneglycols with aliphatic monocarboxylic acids, adipicacid-dialkyl ester, and dibenzoates of alkylene- and polyalkyleneglycols.
 37. A film according to claim 19, wherein said film furthercontains one or more additives selected from oxidation stabilizers, UVstabilizers, dyestuffs, filler materials, pigments and/or anti-adhesionagents.
 38. A coating according to claim 21, wherein said coatingfurther contains one or more additives selected from polymer resins,softeners, pigments, filler materials, stabilizers, adhesion promoters,rheological aids, additives that influence pH, and additives thatcatalyze chemical reactions between the polyvinylacetals and otherpolymer resins.